iOS 如何画圆

在iOS开发的时候，我们可以借助UIBezierPath和CAShapeLayer这两个类来实现画圆的需求，另外我们还可以给圆设置颜色、宽度，设置画圆的动画可以借助CABasicAnimation来实现。下面是代码实现部分。

CGRect rect = CGRectMake(100, 100, 100, 100);

    
    UIBezierPath *beizPath=[UIBezierPath bezierPathWithRoundedRect:rect cornerRadius:50];
    //先画一个圆
    CAShapeLayer *layer=[CAShapeLayer layer];
    layer.path=beizPath.CGPath;
    layer.fillColor=[UIColor clearColor].CGColor;//填充色
    layer.strokeColor=[UIColor redColor].CGColor;//边框颜色
    layer.lineWidth=6.0f;
    layer.lineCap=kCALineCapRound;//线框类型
    [self.view.layer addSublayer:layer];
    
    
    CABasicAnimation *animation=[CABasicAnimation animationWithKeyPath:@"strokeEnd"];
    animation.fromValue=[NSNumber numberWithFloat:0.0f];
    animation.toValue=[NSNumber numberWithFloat:toValue];
    animation.duration=2.0;
    
    //animation.repeatCount=HUGE;//永久重复动画
    //animation.delegate=self;
    //removedOnCompletion：默认为YES，代表动画执行完毕后就从图层上移除，图形会恢复到动画执行前的状态。如果想让图层保持显示动画执行后的状态，那就设置为NO，不过还要设置fillMode为kCAFillModeForwards
    //fillMode：决定当前对象在非active时间段的行为.比如动画开始之前,动画结束之后
    //autoreverses:动画结束时是否执行逆动画
    //timingFunction:设定动画的速度变化
    //kCAFillModeBackwards 可以让动画闭合
    //kCAFillModeForwards  动画不会闭合
    animation.fillMode=kCAFillModeForwards;
    animation.removedOnCompletion=NO;
    animation.timingFunction=[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];

    [layer addAnimation:animation forKey:@"animation"];

另外我们可能还会有一部分的特殊动画效果需要我们来实现，就像雷达波纹效果、不规则图形划线这样的设置，这里也是有办法来实现的。

实例如下：

_testView=[[UIView alloc] initWithFrame:CGRectMake(30, 300, 100, 100)];
    [self.view addSubview:_testView];
    
    _testView.layer.backgroundColor = [UIColor clearColor].CGColor;
    //CAShapeLayer和CAReplicatorLayer都是CALayer的子类
    //CAShapeLayer的实现必须有一个path，可以配合贝塞尔曲线
    CAShapeLayer *pulseLayer = [CAShapeLayer layer];
    pulseLayer.frame = _testView.layer.bounds;
    pulseLayer.path = [UIBezierPath bezierPathWithOvalInRect:pulseLayer.bounds].CGPath;
    pulseLayer.fillColor = [UIColor redColor].CGColor;//填充色
    pulseLayer.opacity = 0.0;
    
    //可以复制layer
    CAReplicatorLayer *replicatorLayer = [CAReplicatorLayer layer];
    replicatorLayer.frame = _testView.bounds;
    replicatorLayer.instanceCount = 4;//创建副本的数量,包括源对象。
    replicatorLayer.instanceDelay = 1;//复制副本之间的延迟
    [replicatorLayer addSublayer:pulseLayer];
    [_testView.layer addSublayer:replicatorLayer];
    
    CABasicAnimation *opacityAnima = [CABasicAnimation animationWithKeyPath:@"opacity"];
    opacityAnima.fromValue = @(0.3);
    opacityAnima.toValue = @(0.0);
    
    CABasicAnimation *scaleAnima = [CABasicAnimation animationWithKeyPath:@"transform"];
    scaleAnima.fromValue = [NSValue valueWithCATransform3D:CATransform3DScale(CATransform3DIdentity, 0.0, 0.0, 0.0)];
    scaleAnima.toValue = [NSValue valueWithCATransform3D:CATransform3DScale(CATransform3DIdentity, 1.0, 1.0, 0.0)];
    
    CAAnimationGroup *groupAnima = [CAAnimationGroup animation];
    groupAnima.animations = @[opacityAnima, scaleAnima];
    groupAnima.duration = 4.0;
    groupAnima.autoreverses = NO;
    groupAnima.repeatCount = HUGE;
    [pulseLayer addAnimation:groupAnima forKey:@"groupAnimation"];

这里的_testview就是测试view通过对这个view的操作设置来实现雷达波纹扩散的效果。

不规则图形的划线的实例如下：

    UIView *line=[[UIView alloc] initWithFrame:CGRectMake(0, 100, 400, 1)];
    line.backgroundColor=[UIColor grayColor];
    [self.view addSubview:line];
    
    _testView1=[[UIImageView alloc] initWithFrame:CGRectMake(0, 100, 300, 200)];
    _testView1.userInteractionEnabled=YES;
    [self.view addSubview:_testView1];
    
    
    //贝塞尔曲线,以下是4个角的位置，相对于_testView1
    CGPoint point1= CGPointMake(10, 80);
    CGPoint point2= CGPointMake(10, 200);
    CGPoint point3= CGPointMake(300, 200);
    CGPoint point4= CGPointMake(300, 80);
    
    _path=[UIBezierPath bezierPath];
    [_path moveToPoint:point1];//移动到某个点，也就是起始点
    [_path addLineToPoint:point2];
    [_path addLineToPoint:point3];
    [_path addLineToPoint:point4];
    //controlPoint控制点，不等于曲线顶点
    [_path addQuadCurveToPoint:point1 controlPoint:CGPointMake(150, -30)];
    
    CAShapeLayer *shapeLayer=[CAShapeLayer layer];
    shapeLayer.path=_path.CGPath;
    shapeLayer.fillColor=[UIColor clearColor].CGColor;//填充颜色
    shapeLayer.strokeColor=[UIColor orangeColor].CGColor;//边框颜色
    [_testView1.layer addSublayer:shapeLayer];
    
    //动画
    CABasicAnimation *pathAniamtion = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];
    pathAniamtion.duration = 3;
    pathAniamtion.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
    pathAniamtion.fromValue = [NSNumber numberWithFloat:0.0f];
    pathAniamtion.toValue = [NSNumber numberWithFloat:1.0];
    pathAniamtion.autoreverses = NO;
    [shapeLayer addAnimation:pathAniamtion forKey:nil];
    
    
    UITapGestureRecognizer *tap=[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(clickk:)];
    [_testView1 addGestureRecognizer:tap];